Support Alpine Linux in main install.sh script with proper package manager detection

[xtetsuji]

Problem

Currently, the main install.sh script is hardcoded to use apt-get for package installation, which causes failures on Alpine Linux and other non-Debian/Ubuntu systems. While we have a separate alpine/install_alpine.sh, the main installation script should handle different Linux distributions gracefully.

When install.sh is executed automatically by GitHub (e.g., in Actions or Codespaces), it fails on Alpine Linux because:

1. apt-get is not available (Alpine uses apk)
2. No fallback mechanism exists for different package managers
3. The script assumes Debian/Ubuntu environment

Current State

• ✅ alpine/install_alpine.sh exists as a separate solution
• ❌ Main install.sh doesn't detect Alpine Linux
• ❌ No package manager abstraction layer
• ❌ Fails when executed automatically on Alpine systems

Proposed Solution

1. Add distribution detection in install.sh

function detect-distro {
    if [ -f /etc/alpine-release ]; then
        echo "alpine"
    elif command -v apt-get >/dev/null 2>&1; then
        echo "debian"
    else
        echo "unknown"
    fi
}

2. Add package manager abstraction

function install-packages {
    local distro=$(detect-distro)
    case "$distro" in
        alpine)
            if command -v apk >/dev/null 2>&1; then
                sudo apk add --no-cache "${INSTALL_PACKAGES_ALPINE[@]}"
            else
                echo "Warning: apk not available, skipping package installation"
            fi
            ;;
        debian)
            sudo apt-get update && sudo apt-get install -y "${INSTALL_DEB_PACKAGES_IN_CODESPACES[@]}"
            ;;
        *)
            echo "Warning: Unknown distribution, skipping package installation"
            ;;
    esac
}

3. Define Alpine package equivalents

declare -a INSTALL_PACKAGES_ALPINE=(
    tig
    bat
    # Note: rcm might not be available, need alternative approach
)

Package Mapping Strategy

Debian/Ubuntu	Alpine	Notes
tig	tig	✅ Available
bat	bat	✅ Available
rcm	❌	Need alternative or skip

For rcm (dotfiles manager), we could:

• Option A: Skip rcm installation and use manual symlink approach
• Option B: Implement basic rcm-like functionality in the script
• Option C: Check if rcm can be installed from edge/testing repos

Benefits

• ✅ Single install.sh works across distributions
• ✅ Graceful degradation when packages unavailable
• ✅ No breaking changes to existing functionality
• ✅ Better CI/CD compatibility

Out of Scope

• RedHat/CentOS support (as requested)
• Complex package manager features
• Perfect feature parity across distributions

Implementation Notes

The goal is to make install.sh resilient rather than feature-complete. If Alpine-specific packages aren't available, the script should warn and continue rather than fail.